The present invention relates to a fluid machine such as a pump, a compressor, and an expansion machine and, more particular, to a displacement type fluid machine.
As a displacement type fluid machine, there have been conventionally known a reciprocating fluid machine which moves a working fluid by repeated reciprocating motion of a piston in a cylindrically shaped cylinder, a rotary type (rolling piston type) fluid machine which moves a working fluid by eccentric rotational motion of a piston in a cylindrically shaped cylinder, and a scroll type fluid machine which moves a working fluid by engaging a pair of a fixed scroll and an orbiting scroll having a spiral wrap erected on an end plate and by revolving the orbiting scroll.
The reciprocating fluid machine has an advantage that it is easy to manufacture and less costly because the construction thereof is simple. However, it has a problem in that the performance is decreased due to the increase in pressure loss because a process from the completion of suction to the completion of discharge is as short as 180xc2x0 in terms of the rotation angle of driving shaft, so that the flow velocity in the discharge process is high. It also has a problem in that vibration and noise are great because a motion for reciprocating the piston is needed, so that the unbalanced inertia force of the driving shaft system cannot be balanced.
Also, the rotary type fluid machine has a less problem in that the pressure loss increases in the discharge process because a process from the completion of suction to the completion of discharge is 360xc2x0 in terms of the rotation angle of driving shaft. However, like the reciprocating fluid machine, it also has a problem in that vibration and noise are great because the fluid is discharged once every one rotation of shaft, so that the fluctuations in gas compression torque are relatively large.
Further, the scroll type fluid machine has an advantage that the pressure loss in the discharge process is low because a process from the completion of suction to the completion of discharge is 360xc2x0 or longer in terms of the rotation angle of driving shaft (normally about 900xc2x0 for the machine practically used for air conditioning), and vibration and noise are low because a plurality of working chambers are generally formed, so that the fluctuations in gas compression torque during one rotation are small. However, a clearance between spiral wraps in a wrap engaging state and a clearance between the end plate and a wrap tip must be controlled, which leads to a problem in that highly accurate machining is needed, which increases the machining cost. Also, the scroll type fluid machine has a problem in that a process from the completion of suction to the completion of discharge is as long as 360xc2x0 or longer in terms of the rotation angle of driving shaft and internal leakage increases as the period for compression process increases.
JP-A-55-23353 (Literature 1), U.S. Pat. No. 2,112,890 (Literature 2), JP-A-5-202869 (Literature 3), and JP-A-6-280758 (Literature 4) have proposed a type of a displacement type fluid machine which carries a working fluid by a revolving motion with a substantially constant radius without the relative rotation of a displacer for moving the working fluid with respect to a cylinder into which the working fluid is sucked, that is, by an orbital motion. The displacement type fluid machine proposed therein comprises a displacer having a petal shape in which a plurality of members (vanes) extend radially from the center, and a cylinder having a hollow portion having a figure substantially similar to the displacer. The working fluid is moved by the orbital motion of the displacer in the cylinder.
In the displacement type fluid machine shown in the Literatures 1 to 4, the imbalance of the driving shaft system can be balanced because the machine has no reciprocating part unlike the reciprocating fluid machine. Therefore, the machine has an advantage that vibration is low, and the frictional loss can be made relatively low because the relative sliding velocity between the displacer and the cylinder is low.
However, a process from the completion of suction to the completion of discharge in an individual working chamber formed by the plurality of vanes composing the displacer and the cylinder is as short as about 180xc2x0 (210xc2x0) in terms of the rotation angle xcex8c of driving shaft (about half of that of the rotary type and nearly the same as that of the reciprocating type), which presents a problem in that the flow rate of the fluid in the discharge process increases and the pressure loss increases, resulting in a decrease in performance. Also, in the fluid machine shown in these literatures, the rotation angle of driving shaft is small in a period from the completion of suction to the completion of discharge in the individual working chamber, and there is a time shift (time lag) from the time when the discharge of working fluid is completed to the time when the next (compression) process begins (completion of suction). Therefore, the mechanical balance is poor because the working chamber is formed eccentrically around the driving shaft from the completion of suction to the completion of discharge, so that a rotating moment for rotating the displacer itself excessively acts on the displacer as a reaction force from the compressed working fluid, which is liable to cause a reliability problem such as the friction and wear of the vane.
A displacement type fluid machine that has solved the above problems has been disclosed in JP-A-9-268987, which has been proposed by the inventors of the present invention. In this machine, the inside wall surface of cylinder and the outside wall surface of displacer are formed so that among a plurality of spaces formed between the displacer and the cylinder, the maximum number of the spaces for the process from the completion of suction to the completion of discharge becomes a predetermined number, whereby the fluid loss is decreased. However, sufficient consideration has not been given to decrease the internal leakage of working fluid at the seal point of the cylinder and the displacer and to enhance the assembling ability and reliability of parts.
In the scroll type fluid machine, as means for decreasing the internal leakage between the wraps of the fixed scroll and the orbiting scroll, a mechanism has been known which allows the movement of the orbiting scroll in the radial outside direction and brings the wraps of the fixed scroll and the orbiting scroll into sealing contact. For example, Japanese Patent Publication No. 2689659 (Literature 5), Japanese Patent Publication No. 2690810 (Literature 6), etc. have disclosed this mechanism.
The internal leakage decreasing mechanism for the scroll type fluid machine shown in the Literatures 5 and 6 shows an example applied to a cantilever type construction in which the driving shaft does not penetrate the orbiting scroll, a movable part, and the driving shaft is supported on one side of the compression element portion. A both-end-supported construction in which both ends of the movable part are supported by a bearing is mechanically complex, so that it has a disadvantage that the application of this technique is difficult and the machining cost increases. Also, an Oldham""s ring etc. are generally used to prevent the rotation of the orbiting scroll, and a mechanism separate from the internal leakage decreasing mechanism is provided, which leads to the increase in the machining manpower, the number of parts, and the cost.
A first object of the present invention is to provide a displacement type fluid machine which is easier to machine and assemble than a scroll type fluid machine and has a low cost and high performance attained by an effective decrease in internal leakage.
A second object of the present invention is to provide a highly reliable displacement type fluid machine in which the rotating moment acting on a displacer is decreased to the utmost.
A third object of the present invention is to provide inexpensive orbiting radius variable means.
The above first object is attained by providing a displacement type fluid machine in which a displacer and a cylinder are disposed between end plates, one space is formed by the inside wall face of the cylinder and the outside wall face of the displacer when the center of the cylinder and the center of the displacer are aligned with each other, and a plurality of spaces are formed when the positional relationship between the displacer and the cylinder is formed so as to be an orbiting position, wherein there is provided driving means in which the orbiting radius of the orbital motion of the displacer changes along the shape of a movement line contact portion of the inside wall face of the cylinder and the outside wall face of the displacer at the time of actual operation.
The above second object is attained by providing a displacement type fluid machine comprising a cylinder having an inside wall composed of a curve such that a planar shape is continuous between end plates, and a displacer having an outside wall provided so as to be opposed to the inside wall of the cylinder, which is formed with a plurality of spaces by the inside wall, the outside wall, and the end plates at the time of orbital motion, wherein there is provided driving means in which when the displacer is revolved to compress a working fluid, part of a bearing load applied to a driving bearing of the displacer is applied as a seal force at a seal point between the displacer and the cylinder, and the planar shapes of the inside wall of the cylinder and the outside wall of the displacer are formed so as to be an alternating moment in which the direction of a rotating moment acting on the displacer is changed over.
The above third object is attained by providing a displacement type fluid machine comprising a cylinder having an inside wall composed of a curve such that a planar shape is continuous between end plates, a displacer having an outside wall provided so as to be opposed to the inside wall of the cylinder, which is formed with a plurality of spaces by the inside wall, the outside wall, and the end plates at the time of orbital motion, and a driving shaft for driving the displacer, wherein there are provided the driving shaft which has an eccentric portion formed with a planar portion in which the outside diameter face is partially cut away, and a substantially segment shaped slider having a partial cylinder shape which slides in engagement with the planar portion of the driving shaft and has a oil film pressure generating portion for supporting a load applied to a displacer driving bearing.